The present invention relates to an improved gas liquefying and storage system, and especially to a system for storing a gas whose principal ingredient is methane by mixing the gas with another hydrocarbon (an organic solvent) for storage.
Until now, there have been several different methods for storing methane or a gas, such as natural gas, whose principal ingredient is methane. For example, storing the gas by compression under a high pressure or by adsorption to an adsorbent are both possible methods. In addition, methods have been proposed in which methane is dissolved in a composite hydrogen solvent such as propane, butane, etc. and then stored in a liquid state. For example, U.S. Pat. No. 5,315,054 discloses such a methane liquefying and storing method.
The disclosure of U.S. Pat. No. 5,315,054, however, only describes that methane could be stored by simply dissolving it in a hydrocarbon solvent. This method is not sufficient for storing methane with a high density.
Furthermore, there is no disclosure of a method for discharging methane, or gas whose principal ingredient is methane, with a constant ratio of constituents. When the ratio of the constituents of the gas or liquid discharged from a storage container is not constant, disadvantages, such as variation in flammability and unstable combustion in an internal engine or the like, are experienced.
The present invention addresses problems posed with the prior art and its object is to provide a gas liquefying and storage system for a gas whose principal ingredient is methane, making it possible to store methane with a high density and to discharge stored material while maintaining a constant ratio of constituents.
To attain the above-described object, the present invention provides a gas liquefying and storage system for methane-base gas (gas whose principal ingredient is methane), for dissolving such gas in a hydrocarbon solvent for storage in a storage container and discharging stored material from the storage container for use. This system is furnished with a composition adjusting means for maintaining constant rates of the constituents of stored material being discharged.
The composition adjusting means included in the above system maintains constant rates of the constituent elements of the contents of the storage container.
A hydrocarbon solvent that is applied to the above system is a hydrocarbon that is liquid at room temperature.
A hydrocarbon solvent that is also applied to the above system is a composite solvent of a hydrocarbon that does not readily liquefy at room temperature and a hydrocarbon that is liquid at room temperature.
Hexane is a hydrocarbon solvent applicable to the above system.
Gasoline or light oil is also a hydrocarbon solvent applicable to the above system.
Dimethyl ether is also a hydrocarbon solvent applicable to the above system.
In the above system, a super-critical state exists in the storage container at least during an initial period of discharge of the stored material.
In the above system, the ratio of the constituent elements of the contents of the storage container may be such that a hydrocarbon of a carbon number of 3 or higher is between 7% and 45%, while a hydrocarbon of a carbon number of 2 or lower is between 93% and 55%.
In another aspect of the above system, the ratios of the constituent elements of the contents of said storage container may be such that a hydrocarbon of a carbon number of 3 or higher is between 7% and 65%, while a hydrocarbon of a carbon number of 2 or lower is between 93% and 35%.
Butane is applicable to the above system as the principal hydrocarbon ingredient of with a carbon number of 3 or higher.
Propane is also applicable to the above system as the principal hydrocarbon ingredient of with a carbon number of 3 or higher.
In the above system, the storage container may be temperature-regulated such that its internal super-critical state will be maintained.
The above system may preferably include a means for determining the conditions in the storage container in order to determine the ratio of the constituents of the hydrocarbon and the quantity of the hydrocarbon contained in the storage container; and a supply ratio control means for calculating a ratio at which the gas whose principal ingredient is methane and the hydrocarbon solvent are supplied to the storage container, based on the result of the above detection and executing the supply.
This supply ratio control means may calculate a supply ratio, based on the supply quantity of the gas bearing methane as the principal ingredient.
The above means for determining the conditions in the storage container will detect pressure, temperature, and solvent solution quantity in the storage container and obtain the ratios of the hydrocarbon constituents and the hydrocarbon quantity from these parameters.
In the above system, the hydrocarbon discharged from said storage container may be oxidized in an internal combustion engine and the means for determining the conditions in the storage container may obtain the ratios of the hydrocarbon constituents, based on the output from an air-fuel ratio determining means provided to the internal combustion engine.
In another aspect of the above system, a vapor-phase outlet is provided at the top of the storage container, a liquid quantity detector is installed to detect the quantity of liquid hydrocarbon solvent in the storage container, just the vapor-phase portion of stored material in the storage container is exclusively discharged through the vapor-phase outlet, and the quantity of hydrocarbon solvent to be supplied for recharging is calculated based on the result obtained by the liquid quantity detector.
In another aspect of the above system, a withdrawal container is installed to receive the withdrawn remaining hydrocarbon from the storage container, and the withdrawn hydrocarbon and the gas whose principal ingredient is methane are supplied after the hydrocarbon solvent is supplied.
In another aspect of the above system, a temporary charging container is connected to the storage container, the hydrocarbon solvent is supplied to this temporary charging container before the gas whose principal ingredient is methane, and the gases are supplied together to the storage container.
In another aspect of the above system, a temporary charging container for exclusive solvent use is installed in parallel connection with the storage container so as to be positioned higher than the liquid level of the storage container via piping equipped with a means of controlling passage; the temporary charging container for exclusive solvent use is charged with the hydrocarbon solvent while the passage is closed, and the hydrocarbon solvent enters the storage container when the passage is opened.
In another aspect of the above system, a storage container is installed on a mobile body and a hydrocarbon solvent-dedicated storage container for storing only the hydrocarbon solvent is connected to this storage container.
In another aspect of the above system, material stored in gas is discharged from the vapor-phase portion of the storage container and the hydrocarbon solvent in liquid phase is separated from the discharged gas and returned to the storage container.
In another aspect of the above system, material stored in a liquid is discharged from the liquid-phase portion of the storage container in a small amount such that no substantial change of internal pressure of said storage container occurs and the discharged liquid is returned to the storage container after the vaporization of gas whose principal ingredient is methane from the liquid.
In the above system, the vapor-phase hydrocarbon may be discharged from the top of the storage container and the liquid-phase hydrocarbon may be discharged from the bottom of the storage container at a constant ratio.
The storage container in the above system may be furnished with a liquid quantity detector.
In another aspect of the above system, the stored material discharged from the storage container oxidized in an internal combustion engine and the means for determining the conditions in the storage container obtains the ratios of the hydrocarbon constituents, based on the output from an air-fuel ratio determining means provided to the internal combustion engine.
In the above system, the discharged vapor-phase and liquid-phase hydrocarbons may be heated to blend together.
In the above system, the discharged liquid-phase hydrocarbon may be vaporized and then blended together with the discharged vapor-phase hydrocarbon.
In the above system, the storage container may be cooled while being supplied with said gas.
In another aspect of the above system, the storage container is furnished with a plurality of charging ports positioned apart from each other, and, during the charging with a gas whose principal ingredient is methane, one charging port may initially be used and then the charging may be switched to another charging part.
In another aspect of the above system, the storage container is furnished with a heat conducting means covering the inner surface of the storage container and connected to a charging port for a gas whose principal ingredient is methane, said charging port provided on the storage container.
In another aspect of the above system, the storage container is furnished with a plurality of charging ports positioned apart from each other and the charging ports may be used at the same time.
In another aspect of the above system, a passage extension member extending from a charging port provided on the storage container and entering the internal space of the container is installed, and this passage extension member has a plurality of release openings arranged along its longitudinal direction so as to be adequately separated from the inner walls of the container.
These release openings may be angled as internal outlets of a charging port provided on the storage container.
In the above system, a charging port may be positioned at the far end from the area that holds the solvent in the storage container.
In the above system, a porous body may be fit in the storage container.
With the above system, charging may be performed such that the use of a charging port provided at the bottom of said storage container may begin while gas is being charged.
In another aspect of the above system, a portion of the hydrocarbon solvent is vaporized and released outside the storage container before the storage container is charged with a gas whose principal ingredient is methane.
In the above system, stored material may be released outside the storage container via a decompression passage provided inside or on the surface of the storage container.
This decompression passage may be covered with heat-regenerative material.
The above system can be charged with a cooled hydrocarbon solvent before being charged with gas whose principal ingredient is methane.
The storage container in the above system may be furnished with an agitating means.
In another aspect of the above system, the hydrocarbon solvent can be discharged from the storage container for urgent use.
Furthermore, the invention provides a gas liquefying and storage device for gas whose principal ingredient is methane comprising a composition information determining means for determining the ratios of the constituents of material stored in the storage container in which a gas whose principal ingredient is methane is dissolved in a hydrocarbon solvent and stored; and a sending means for sending the result of the above detection to the supply side from which the gas and the hydrocarbon solvent are supplied to the storage container.
Furthermore, the invention provides a gas liquefying and storage device for gas whose principal ingredient is methane, said device comprising a withdrawal container for withdrawing the remaining hydrocarbon from a storage container in which a gas whose principal ingredient is methane is dissolved in a hydrocarbon solvent and stored; a detection means for determining the rates of the constituents of the hydrocarbon in the withdrawal container; and a supply ratio control means for controlling a ratio at which such gas and the hydrocarbon solvent are supplied to the storage container based on the result of the above determination.
Furthermore, the invention provides a gas liquefying and storage device for gas whose principal ingredient is methane, wherein, at a stage preceding a storage container in which a gas whose principal ingredient is methane is dissolved in a hydrocarbon solvent and stored, a temporary charging container for exclusive solvent use is installed via a means for controlling the passage between the storage container and the temporary charging container for exclusive solvent use.
Furthermore, the invention provides a gas liquefying and storage device for gas whose principal ingredient is methane, wherein the supply source of such gas and the supply source of a hydrocarbon solvent are connected, via respective control means, to a temporary storage tank that is in turn connected to a storage container in which a gas whose principal ingredient is methane is dissolved in the hydrocarbon solvent and stored.
Furthermore, the invention provides a gas liquefying and storage device for gas whose principal ingredient is methane comprising a main storage container in which a gas whose principal ingredient is methane is dissolved in a hydrocarbon solvent and stored; and a hydrocarbon solvent-dedicated storage container for storing only the hydrocarbon solvent, wherein said hydrocarbon solvent-dedicated storage container is connected to the main storage container via a control means.
Furthermore, the invention provides a gas liquefying and storage device for a gas whose principal ingredient is methane comprising a vapor-phase outlet for discharging gaseous stored material, provided at the top of a storage container in which such gas is dissolved in a hydrocarbon solvent and stored; a vapor-liquid separator for separating liquid from the discharged gaseous stored material; and a feedback passage for returning the liquid separated through the vapor-liquid separator to the storage container.